Inflatable air bags have been increasingly used in modern automobiles. Together with an inflating means, the air bag is accommodated in a housing. The inflating means is also called a gas generator. The system is ignited via sensors. Extremely strong forces, which widen the housing to the outside in the manner of the mouth of a fish, are partially generated in the area of the outlet of the air bag immediately after the ignition of the gas generator. The greatest expansion takes place approximately in the middle of the area of the free opening of the front chamber. The outlet-side area of this front chamber is also called the shot channel. The fish mouth-like expansion of the shot channel may lead to damage to the surrounding components, which may lead, e.g., in the case of the air bag installed on the passenger side, to the deformation of the entire dashboard and to the need to replace it. This entails costs, which are avoidable.
A great variety of variants of housing designs for inflatable air bags, which are to avoid the fish mouth effect, have been known.
For example, a vehicle air bag module, in which a folded air bag and an inflating means are accommodated together in a housing and are installed in the vehicle as a complete assembly unit, is disclosed in DE-41 41 617 A1. In the solution described in that document, the housing has two compartments: a front compartment and a rear compartment. An inflating means is inserted into the rear compartment. This comprises a cylindrical outer housing, in which a plurality of nozzles are provided. The cylindrical outer housing is called the diffusor. The diffusor is used to accommodated the gas generator. The holes of the diffusor are arranged in the housing of the air bag unit such that a directed discharge of the gas into the air bag can take place. Without a diffusor, the gas would spread out non-uniformly after the gas generator has ignited. However, this would not be desirable, because the air bag must be inflated within fractions of one second reliably, dependably and uniformly in order to function as intended.
The diffusor with the gas generator inserted therein is introduced into a hole in one side wall of the housing and screwed to the opposite housing wall by means of a threaded shaft.
The air bag itself is inserted into a reinforced frame, which is fitted into the housing.
The entire housing construction is composed of a plurality of individual parts in the embodiment shown. The housing is made as a sheet metal part. Besides the fact that manufacture is expensive due to manufacturing reasons, such a housing has the drawback of having a high intrinsic weight.
To compensate these drawbacks, it is proposed in DE 43 38 666 A1 that a housing for an air bag be made of plastic. Plastics make it possible to considerably reduce the weight compared with metallic materials. In addition, the brackets for fastening the housing in the motor vehicle are made in one piece with the plastic housing in the solution shown in this document.